Accurate instrumentation possible on a diesel?

[oldbeaver]

Originally Posted by AndrzejM

Your pump is controlled by two factors:
1. gas pedal linkage - it's setting up rack position - thus main fuel dosage
2. ELR signal - it's changing by some percentage fuel dose to meet value counted by ECU, based on all the sensors

So you have to know rack position adt its offset by ELR signal, then you have the exact fuel dose. Combining that with rpm signal you have the exact moments when you have to measure rack position and offset. Lets call that a trigger signal. And finally combining that with VSS signal will give you FE.

And the other question about Y31 - I presume that's a valve for EGR

Ok, very good. Lets try to get the signals.

Rack position: there is a plug on the back of the governor of the injection pump with three wires. One of these should have the signal we want.

I took a picture of it but forgot how to insert here.

ELR signal: I am searching for it but won´t be difficult.

RPM signal is available in test socket. In this same socket there is an "diesel injection" signal, which I don´t know what is measuring, maybe just that the EDS is working ok.

You said to use RPM as the trigger signal as for when measuring the others, isn´t it?

Wouldn't it be possible to do the following, as an alternative:

Measure the rack position modulated by the ELR signal (surely some of the three wires has it already), and multiply it by the rpm value, for having a measure of how much fuel is being injected?

It would be a analog signal, I think.

I think it as follows: rack position tells how wide open is the gate that governs the passing of fuel (liters/stroke), while RPM tells at how much strokes per second it working the injection pump (strokes/sec).

Multipliying the first times the second should give liters/sec of injection.

Of course there are some constants to calibrate, as the pump may rotate at twice the speed of the engine, and we don´t know how much fuel per stroke each injector injects. But I think I have that info somewhere.

However, the liters/stroke each injector injects in the cylinder is not even at every rpm. It has a range that depends, again, on the RPM.

So, lets try to model that :

Iq = ((a + b*Rack * rpm)) + c*rpm*rpm

where:

Iq = inyected quantity (lts/sec)
a = callibration constant to be corrected with the full tank mileage
b = max injected volumen per stroke specific for the BOSCH pump
c = small value, probable negative, that indicates a limit vs RPM
Rack = rack position already modulated

How do you like it?

My intuition tells me it maybe less accurate, but simpler in the sense I think I can do it. While I don´t see how to materialize yr method. Maybe if you explain a Little more?


Best,

OldBeaver


VSS signal: I will see in which place I will get it.

[AndrzejM]

Jose,

You can't measure constantly any values here so you need a trigger to measure fuel dose at the injection pump. That's why you need rpm signal. It's a trigger for the moment that you should look into other signals from the IP.


That's an example of fuel dose. Rack position is combined with an ELR offset and that gives you exact fuel dosage. Measuring those two values at the moment of trigger signal (rpm) gives you the amount of fuel per one rpm. Changing this to time of injection pulse gives you proper signal for MPGuino.

So you don't need any pump specific volumes. You just need to calibrate it properly and voila!

[oldbeaver]

Originally Posted by AndrzejM

Jose,

You can't measure constantly any values here so you need a trigger to measure fuel dose at the injection pump. That's why you need rpm signal. It's a trigger for the moment that you should look into other signals from the IP.


That's an example of fuel dose. Rack position is combined with an ELR offset and that gives you exact fuel dosage. Measuring those two values at the moment of trigger signal (rpm) gives you the amount of fuel per one rpm. Changing this to time of injection pulse gives you proper signal for MPGuino.

So you don't need any pump specific volumes. You just need to calibrate it properly and voila!

Dear AndrzejM,

I try hard to understand and follow yr thoughts, but I cannot do it fully.

RPM is also a signal that is present at every moment. When shall we consider that it is triggering the measure of Rack + ELR? Are you talking of sampling signal values?

Let me think: we have one injection per cylinder every two turns of the engine, right? Equals 0,5 injections per turn per cylinder. If so, as we have 6 cylinders, then we have: 0,5 * 6 = 3 injections per turn of the engine.

So you want to sample (measure) rack position 3 times per revolution, and just in the moment injection is produced? Is that the idea? And how do you do that?

I am very slow today but I perceive you have a very clear idea in mind, but not how it Works. But my interest increase any minute.

Thank you for the graphic and the explanation, but I still don´t follow you.
I lack of knowledge for it. Please. try to express it even simpler, if posible.

Looking forward for it,

Old Beaver

[AndrzejM]

Hi Jose,

Sorry for late response (I've seen your e-mail), but I was on a holidays with no internet access. Anyway I'll take a look at your document and get back to you ASAP.

I was thinking about this issue during my free time and I think I have some answers.

Cheers

[oldbeaver]

Originally Posted by AndrzejM

Hi Jose,

Sorry for late response (I've seen your e-mail), but I was on a holidays with no internet access. Anyway I'll take a look at your document and get back to you ASAP.

I was thinking about this issue during my free time and I think I have some answers.

Cheers

Thank you! I look forward to it.

[oldbeaver]

Originally Posted by NedTheHead

The promotional material for the ScanGauge II indicates that it supports diesels. Is that just wrong? Or is there something about my truck that's unsupported. Still confused here...

Yes, Scangauge is supporting some diesels. But they are only OBDII compliant diesels. Don´t know if ANY OBDII compliant diesels.

We are trying to develop instrumentation for old diesels.

Oldbeaver

[cRiPpLe_rOoStEr]

Originally Posted by oldbeaver

Yes, Scangauge is supporting some diesels. But they are only OBDII compliant diesels. Don´t know if ANY OBDII compliant diesels.

Wait a minute. Isn't your Skoda OBD2-compliant?

[oldbeaver]

Originally Posted by cRiPpLe_rOoStEr

Wait a minute. Isn't your Skoda OBD2-compliant?

Ha, ha, ha.... I surely said it not very clear. Of course Skoda 2009 is OBDII compliant and it has a Factory installed very powerful trip computer and diag socket. There is even a special diag software for all VAG group.

The fact is that I am working for my 1993 MBZ turbo diesel, 6L, engine OM603 on a W124 chassis. And that old car isn´t OBDII compliant.

There are many as it, many other diesel cars and jeeps and trucks, in the same situation. If they had a trip computer, they would have been able to test any mod and improvement in real time mpg, which is the best overall indicator . So developing one would be very interesting.

Best,

OldBeaver

[oldbeaver]

Originally Posted by oldbeaver

Dear AndrzejM,

I try hard to understand and follow yr thoughts, but I cannot do it fully.

RPM is also a signal that is present at every moment. When shall we consider that it is triggering the measure of Rack + ELR? Are you talking of sampling signal values?

Let me think: we have one injection per cylinder every two turns of the engine, right? Equals 0,5 injections per turn per cylinder. If so, as we have 6 cylinders, then we have: 0,5 * 6 = 3 injections per turn of the engine.

So you want to sample (measure) rack position 3 times per revolution, and just in the moment injection is produced? Is that the idea? And how do you do that?

I am very slow today but I perceive you have a very clear idea in mind, but not how it Works. But my interest increase any minute.

Thank you for the graphic and the explanation, but I still don´t follow you.
I lack of knowledge for it. Please. try to express it even simpler, if posible.

Looking forward for it,

Old Beaver

Dear AndrzejM,

On our email conversations, we come to the fact that it is possible to get the necessary signals from a 1993 MBZ diesel turbo, non OBDII compliant, for feeding a MPGuino trip computer.

In brief:

VSS signal is available in Mercedes and possibly in any old diesel. Or can be taken from a GPS.

Fuel injection signal will be obteined from Governor + ECU and rpm.

Sampling will be triggered by revolution sensor.

To make a signal that is suitable for MPGuino, we need to process it a little bit, before input it to that board.

Y have a old MPguino, very well assembled, with English units which carries a ATMega168 processor. I tried to load to it the Canadian version of the software but it has not enough memory for that.

Due to that, I bought a ATMega 368 processor thinking in swapping it in the MPGuino, having this way a lot more memory, which we eventually may use for the additional code needed.

I also have a programmer which carries a ATMega368 also.

And I have a FreeDuino board, however, with no parts, empty. All bought in the US by mail a couple of years ago.

Bellow I attached small pictures of all these parts.

What is the best way to accomplish our objectives, from the hardware point of view?

Oldbeaver

[AndrzejM]

Jose,
For the beginning you don't have to change MPGuino to get metric code working or to upgrade any code. First we need to get it work just for a proof of concept.
For conversion unit I think the best would be to use ATtiny. It's small, energy efficient and it can be fitted anywhere.
Then you can try to rebuild your MPGuino to get any code you want working and with conversion unit attached.